GB929576A - Apparatus for deriving television signals from cinematographic film - Google Patents

Abstract

929,576. Automatic registration control. BUSH & RANK CINTEL Ltd. Jan. 11, 1961 [Jan. 11, 1960], No. 954/60. Class 38 (4). [Also in Groups XX and XL (b)] In television apparatus for scanning a continuously moving kinematograph film 1 with the aid of a cathode-ray tube flying-spot scanner 6 so as to generate a picture signal in a photo-electric cell 45, the image 5 of the raster from the flying-spot scanner, which is formed on the film by a lens 7, is maintained in register with a film frame by means of an electromagnetic deflector 9 (see Group XX) which is actuated by a current wave from a generator 10. In accordance with a feature of the invention, departure of the raster from correct registration is detected photo-electrically and an error signal applied to restore registration. In one way of doing his, light from a source 11 illuminates the sprocket holes at one side of the film and an image 21, Fig. 2, of one hole is formed on an apertured mask 14 by way of deflector 9 and lens 7. Behind the mask is a photo-electric cell 18. The image is arranged so that normally half the image is exposed to the photo-electric cell. Any departure of deflector 9 from the correct position to maintain register results in a variation of the illumination of the cell and the production of an error signal. A second photoelectric cell 17 located behind an aperture 15 is arranged to receive light from source 11 by way of an unperforated part of the film so as to furnish a reference signal. The error signal, which is derived by circuit 20 as the difference between the outputs of cells 17 and 18, is applied through a mixer circuit 41 so as to control generator 10, and is also applied through a circuit 22 to the deflector coils 23 of flying-spot scanner 6 so as to shift the raster position. This latter operation effects an instantaneous correction for misregistration whereas correction applied to deflector 9 is delayed due to the inertia of the deflector. In another way of detecting misregistration, Fig. 3 (not shown), photo-electric cell 18 is arranged to receive light reflected from small reflecting elements carried on the sprocket which traverses the film and located (preferably adjustably) at intervals corresponding to the height of one film frame. Reference is made to an arrangement in which photo-electric cell 18 is replaced by a pair of cells which are differentially illuminated by the light from the sprocket hole or reflecting element.